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allow type params before navigation suffix #79

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allow type params before navigation suffix #79

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17 changes: 10 additions & 7 deletions grammar.js
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Original file line number Diff line number Diff line change
Expand Up @@ -84,13 +84,13 @@ module.exports = grammar({
[$._postfix_unary_expression, $._expression],

// ambiguity between generics and comparison operations (foo < b > c)
[$.call_expression, $.prefix_expression, $.comparison_expression],
[$.call_expression, $.range_expression, $.comparison_expression],
[$.call_expression, $.elvis_expression, $.comparison_expression],
[$.call_expression, $.check_expression, $.comparison_expression],
[$.call_expression, $.additive_expression, $.comparison_expression],
[$.call_expression, $.infix_expression, $.comparison_expression],
[$.call_expression, $.multiplicative_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.prefix_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.range_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.elvis_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.check_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.additive_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.infix_expression, $.comparison_expression],
[$.call_expression, $.navigation_expression, $.multiplicative_expression, $.comparison_expression],
[$.type_arguments, $._comparison_operator],

// ambiguity between prefix expressions and annotations before functions
Expand All @@ -113,6 +113,7 @@ module.exports = grammar({

// ambiguity between parameter modifiers in anonymous functions
[$.parameter_modifiers, $._type_modifier],

],

externals: $ => [
Expand Down Expand Up @@ -673,6 +674,8 @@ module.exports = grammar({
indexing_suffix: $ => seq("[", sep1($._expression, ","), "]"),

navigation_suffix: $ => seq(
// this introduces ambiguities with 'less than' for comparisons
optional($.type_arguments),
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Hm, I'm not quite sure how I feel about this workaround. While I understand that it's hard to parse, it seems to deviate quite a bit from the reference grammar and including the type arguments in the navigation suffix node (both of which are exposed), downstream consumers might have to rewrite the syntax tree quite a bit to get accurate results.

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I suppose it just comes down to how much you weigh being able to parse this versus the compromises we've already made with the syntax tree. For instance, this call_suffix workaround (which basically does the same thing, by embedding the optional type arguments in a different node of the tree) was worthy enough of being included, so I see this as adding just another case.

I can keep thinking about it, but this seems like a rather pervasive parsing issue, from the things I've seen, and I'm not sure if we can make something truly faithful to the original syntax specification. At the end of the day, the Kotlin grammar is a reference for specification, but implementation may face some difficulties emulating it.

$._member_access_operator,
choice(
$.simple_identifier,
Expand Down
19 changes: 19 additions & 0 deletions src/grammar.json
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Original file line number Diff line number Diff line change
Expand Up @@ -3316,6 +3316,18 @@
"navigation_suffix": {
"type": "SEQ",
"members": [
{
"type": "CHOICE",
"members": [
{
"type": "SYMBOL",
"name": "type_arguments"
},
{
"type": "BLANK"
}
]
},
{
"type": "SYMBOL",
"name": "_member_access_operator"
Expand Down Expand Up @@ -6133,36 +6145,43 @@
],
[
"call_expression",
"navigation_expression",
"prefix_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"range_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"elvis_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"check_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"additive_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"infix_expression",
"comparison_expression"
],
[
"call_expression",
"navigation_expression",
"multiplicative_expression",
"comparison_expression"
],
Expand Down
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